variable scope problem in android

Question

hi all i have an arraylist and array in an activity and have two function. i declared arraylist and array in activity and used in a function. but i cannot access in those variables in second function. both function is in same activity. in second function gives NullPointerException in Logcat. code:

public class testapplication extends Activity {
 ArrayList<String> getdatabase = new ArrayList<String>();
 public  String[] array;
 protected void onStart() {
      getdatabase.add("1");
      getdatabase.add("2");
      array=new String[getdatabase.size()];
      getdatabase.toArray(array);
      Log.e("app",""+array.length()); // print as app  2

   }

 public void onCreate(Bundle savedInstanceState) {

 Log.e("app",""+array.length()); // NullPointerException.
 }

}

please help me.

According to Activity life cycle,onCreate is called before onStart, so you do the code in onCreate rather than onStart() and i want to know any particular reason for doing it in onStart() — Sankar Ganesh PMP
– Sankar Ganesh PMP, Commented Apr 26, 2011 at 8:34

RoflcoptrException · Accepted Answer · 2011-04-26 07:15:03Z

3

The problem is that onCreate() is the method that is first called if your Activity starts. At this point, you haven't yet initialized your variable array. That's why you get a NullPointerException there.

To solve the problem you have to assure that you call this:

array=new String[getdatabase.size()];

before you try to access the array.

As coder_tim pointed out, in the documentation you can clearly see that onCreate() is always called before onStart().

answered Apr 26, 2011 at 7:15

RoflcoptrException

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2 Comments

coder_tim Over a year ago

Agreed, check this out: developer.android.com/reference/android/app/Activity.html

RoflcoptrException Over a year ago

Good link, there you can see that onStart is always called after onCreate.

Vladimir Ivanov · Accepted Answer · 2011-04-26 07:15:47Z

0

onStart() is called after onCreate(), so array is not created yet. See here.

answered Apr 26, 2011 at 7:15

Vladimir Ivanov

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Comments

J.S. Taylor · Accepted Answer · 2011-04-26 07:20:13Z

0

Referencing to Android activity life cycle, onCreate is called before onStart, that's why you got NullPointerException Besides, just a heads up. You should call super.onCreate and super.onStart somewhere in the methods you overrided.

answered Apr 26, 2011 at 7:20

J.S. Taylor

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